GWINs: Group-Based Medium Access for Large-Scale Wireless Powered IoT Networks

Abstract

Internet of Things (IoT) provides a framework for interconnecting, controlling and monitoring of real-world objects and smart-devices through sensors. The sensors need energy sources to continuously operate. Since the design and the size constraints may impede a sensor node to have a distinct power source, the Energy Harvesting (EH) techniques emerge to cope with the energy constraint problem. Massive IoT networks with the Radio Frequency (RF) EH capability requires new accessing methods to reduce or mitigate interference and collisions. In this paper, we propose a group-based Medium Access Control (MAC) protocol, where a group head coordinates the corresponding nodes. The group heads working as Hybrid Access Points (HAPs) provide nodes with power and relay their data to the base station (BS). The HAPs use a distributed coordination function (DCF) to access the channel, along with in-group coordinating mechanism. In a group, nodes reduce collisions by using a frame slotted ALOHA to access the medium, with the addition of the EH mechanism. Nodes utilize the harvest-transmit-and-sleep protocol to harvest energy, to transmit information utilizing the harvested energy and to sleep when channel is inactive. We study channel models for different communication environments influencing the usability of RF energy harvesting and examine their impact on the network performance. We aim to mitigate inter-group and intra-group collisions and to provide an energy harvesting and data relaying mechanism in a distributed manner. Performance evaluations are carried out through extensive simulations and the model and analysis are verified. It is shown that the analysis results match well with those of simulations. The proposed distributed group-coordination mechanism achieves significant network performance gain over the conventional schemes. The effectiveness of the proposed scheme is shown by the network throughput, and the energy efficiency. © 2013 IEEE.